Unit 1 Revision Cards AQA Spec A Biology

These are cards to condense the big studied units into quick reminder flashcards when long revision sessions get dull

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What is the difference between a causal connection and a correlation?

A correlation occurs when a change in one of two variables is reflected by a change in the other variable wherease a causal connection means a factor is the cause of the illness.

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Enzymes and digestion

Name the functions of the following:

1. Oesphagus Carries food from mouth to stomach

2. Stomach store and digest foos

3. Small intestine Digestion and absorbtion of digestive products

4. Large intestine Absorbing water to make faeces drier and thicker in consistency

5. Rectum . Allow process of egestion to take place

6. Salivary glands Break down starch into maltose

7. Pancreas Digest proteins, carbodydrates and lipids

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1. What is the test for reducing sugars

2. Method of the test in question 1

1. Benedicts test

2. Add 2cm(cubed) of the food sample to be tested to a test tube

Add an equal volume of Benedicts reagent

Heat the mixture in a gently boiling water bath for five minutes

Look for a brick red colour

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Carbohydrates continued

Disaccharide formation

Which pair of monosaccharides form:

1. maltose

2. sucrose

3. lactose

4. By which reaction do monosaccharides join?


1. glucose and glucose

2. glucose and fructose

3. glucose and galactose

4. condensation

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Biochemical tests

What is the test for a non reducing sugar?

The reducing sugar test is first carried out if the solution remains blue then a reducing sugar isnt present.

Add another 2cm(cubed) of the food sample to 2cm(cubed) of dilute hydrochloric acid in a test tube and place the test tube in a gently boiling water bath. This will hydrolyse any disaccharide present into its monosaccharides.

Slowly add some sodium hydrogencarbonate solution to the test tube in order to neutralise the hydrochloric acid

Re test the solution ny heating it with 2cm(cubed) of Benedicts reagent in a gently boiling water bath for five minutes

If a non reducing sugar was present in the original sample, the Benedicts reagent will now turn orange-brown. This is due to the reducing sugars that were produced from the hydrolysis of the non-reducing sugar.

Why was sodium hydrogencarbonate used?

In order to neutralise the hydrochloric acid, as Benedicts reagent wont work in acidic conditions

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Test for starch

What is the biochemical test for starch?

  • place 2cm(cubed) of the sample into a test tube or add two drops of the sample into a depression onto a spotting tile
  • add two drops of iodine solution and shake or stir
  • the presence of starch is indicated by a blue-black coloration
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Carbohydrate digestion

What are the roles of salivary and pancreatic amylase along with maltase?

Salivary amylase hydrolyses starch into maltose and keeps pH at neutral

Pancreatic amylase hydrolyses remaining starch into maltose and keeps pH at neutral

Maltase hydrolyses maltose from starch breakdown into alpha glucose

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How are peptide bonds formed?

Condensation reaction -OH from carboxyl group (amino acid 1) and -H from amino group (amino acid 2)

What does the primary structure dictate?

shape and function

What bonds form in the secondary structure?

Hydrogen bonds between

What are the three bonds which maintain tertiary structure?

disulfide bonds, ionic bonds, hydrogen bonds

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Induced fit model

Why is the induced fit model a better scientific observation than the lock and key model?


how other molecules can effect enzyme activity

how activation energy is lowered

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Factors affecting enzyme action

What effect does temperature have on enzyme action?

Increases kinetic energy of molecules therefore enzyme and substrate come together more in a given time up to an optimum temperature then the enzyme begins to denature

What effect does pH have on enzyme action?

Enzymes have an optimum pH at pHs higher and lower than this cause enzyme to denaturs

How do they cause the enzyme to denature?

Alters charges on amino acids which make up active site and therefore active site changes shape

Bonds which maintain tertiary structure break and therefore enzyme changes shape

What effect does high substrate concentration on rate of reaction?

None because at intermediate substrate concentration maximum number of enzyme substrate complexes have been formed

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Enzyme inhibitors

Name the two types of enzyme inhibitors?

Competiive and non competitive

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What is the difference between resolution and magnification?

Magnification - how many times bigger the image is when compared to the object

Resolution - minimum distance two objects can be apart to appear as separate objects

What are the three conditions the tissue has got to be kept in:

Cold - to reduce enzyme actitivty

Isotonic - prevent osmotic loss or gain

Buffered - to maintain a constant pH

What is the fluid at the top of the test tube called in ultracentrifugation?


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Electron microscopes

Limitations of scanning and tranmission electron microscopes?

  • whole system must be in a vacuum so living specimens can't be observed
  • a complex staining proces is required and even then the image is in black and white
  • specimen must be extremely thin
  • image may contain artefacts

Transmission electron microscopes have exactly limitations except for the specimen doesn't need to be extremely thin.

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